Block reward cannot even be introduced by a mining super majority with a HF or Soft served HF(What Stolfi is alluding to) . Bitcoin requires the longest valid proof of work chain and the second miners increase the block reward or change any fundamentals of why we love Bitcoin we can quickly discard them and switch algo's. It would represent an act of futility and reckless suicide on their part to even think of attempting such a feat. Stolfi is merely a buttcoiner trolling and spreading fear and doubt where he can.

So , yes, technically anything can be introduced with a soft served HF, but that doesn't mean many users will consider it valid . There would be a mass exodus from the miners if the 21million limit was every changed.